MICI: Virology
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Questions and Answers

What is a significant characteristic of enveloped viruses compared to non-enveloped viruses?

  • Enveloped viruses are more resistant to environmental factors.
  • Enveloped viruses can replicate independently.
  • Enveloped viruses are more fragile than non-enveloped viruses. (correct)
  • Enveloped viruses have a higher rate of mutation.

    • What is the primary form of viral genetic material found in viruses?

  • Polysaccharides
  • Ribosomal RNA
  • Nucleic acids (DNA or RNA) (correct)
  • Protein coats

    • In which step of the viral life cycle does the viral capsid get removed?

  • Penetration
  • Uncoating (correct)
  • Synthesis
  • Attachment

    • Which viral shape is characteristic of the rabies virus?

    <p>Complex</p> Signup and view all the answers

    What type of transmission is characterized by viruses being spread via contaminated surfaces?

    <p>Fomites</p> Signup and view all the answers

    What role do host cell enzymes play in the replication of DNA viruses?

    <p>They assist in transcription and replication of viral DNA.</p> Signup and view all the answers

    Which of the following is a method of viral entry into a host cell for enveloped viruses?

    <p>Endocytosis</p> Signup and view all the answers

    In the context of virus structure, what term refers to the protein shell surrounding the viral genome?

    <p>Capsid</p> Signup and view all the answers

    What is the term for the virus in its extracellular state?

    <p>Virion</p> Signup and view all the answers

    What distinguishes vector transmission from other routes of viral transmission?

    <p>Involves a living organism that transmits the virus.</p> Signup and view all the answers

    What is the main characteristic that distinguishes prions from other infectious agents?

    <p>They induce abnormal folding of normal proteins.</p> Signup and view all the answers

    Which statement accurately describes the relationship between HIV and its target cells?

    <p>HIV specifically targets CD4+ T cells.</p> Signup and view all the answers

    Which disease is NOT caused by prions?

    <p>HIV/AIDS</p> Signup and view all the answers

    What mechanism do non-enveloped viruses exhibit that contributes to their environmental stability?

    <p>They have a robust protein capsid.</p> Signup and view all the answers

    What is the correct sequence of events in the viral life cycle?

    <p>Attachment, penetration, uncoating, transcription, translation, genome replication, assembly, release.</p> Signup and view all the answers

    Which virus is primarily known for airborne transmission?

    <p>Measles</p> Signup and view all the answers

    How do abnormal prions differ structurally from normal prion proteins?

    <p>They have β-pleated sheets instead of α-helices.</p> Signup and view all the answers

    What best describes the antigenic changes in influenza viruses?

    <p>They involve antigenic shift and drift.</p> Signup and view all the answers

    What is the primary method of transmission for prion diseases in humans?

    <p>Ingestion of contaminated tissue.</p> Signup and view all the answers

    Which of the following statements about enveloped viruses is true?

    <p>They are typically more sensitive to environmental conditions.</p> Signup and view all the answers

    Study Notes

    Virus Overview

    • Acellular infectious agents
    • Composed of genetic material (DNA or RNA) within a protein coat (capsid)
    • Unable to carry out metabolism, grow, or reproduce independently, relying on host cells for replication

    Virus Structure and Classification

    • Capsid: Protein shell surrounding the viral genome, composed of protein subunits called capsomeres; capsid and genome together form the nucleocapsid
      • Shapes: Helical (e.g., tobacco mosaic virus), Icosahedral (Polyhedral) (e.g., common cold virus), Complex (e.g., rabies and bacteriophages)
    • Envelope: Acquired from host cell during replication/release, composed of a phospholipid bilayer, enveloped viruses are more fragile than non-enveloped (naked) viruses, which are more resistant to environmental factors such as acids, heat, and detergents

    Viral Life Cycle

    • Steps in Cellular Infection:
      • Attachment: Virus binds to host cell receptors
      • Penetration: Virus enters the host cell, either by fusion (enveloped viruses) or direct penetration/endocytosis (non-enveloped viruses)
      • Uncoating: Capsid is removed, releasing viral nucleic acid
      • Synthesis:
        • DNA Viruses: Use host enzymes for transcription and replication
        • RNA Viruses: Often bring or synthesize RNA polymerase to replicate RNA genomes, as host cells lack enzymes for RNA-to-RNA synthesis
      • Assembly: Viral proteins and nucleic acid are assembled into new virions
      • Release: Non-enveloped viruses lyse the host cell, while enveloped viruses bud out, acquiring their envelope

    Virus Transmission

    • Routes:
      • Direct Contact: E.g., herpes, HIV, influenza
      • Airborne: E.g., measles, chickenpox
      • Fomites: E.g., enteroviruses, noroviruses (transmitted via contaminated surfaces)
      • Vectors: E.g., West Nile virus
      • Vertical Transmission: Mother-to-fetus transmission, e.g., HIV

    Virus-Induced Diseases and Key Examples

    • Measles: Airborne transmission, causes rashes, fever, can lead to complications like encephalitis
    • HIV: Bloodborne, targets CD4+ cells; associated with opportunistic infections due to immunosuppression
    • Influenza: Transmitted via droplets; antigenic shift and drift contribute to new strains and pandemics

    Prions: Structure and Pathology

    • Infectious proteins lacking nucleic acids, capable of inducing normal proteins to refold abnormally
    • Mechanism:
      • Normal cellular prion proteins (PrP^C) contain α-helices
      • Abnormal prions (PrP^Sc) have β-pleated sheets and convert normal proteins into the diseased form upon contact
    • Transmission and Resistance:
      • Spread via ingestion of contaminated tissue, especially nervous tissue
      • Resistant to standard sterilization; require incineration or specialized enzyme treatments
    • Diseases:
      • Human: Creutzfeldt-Jakob disease, kuru
      • Animal: Mad cow disease (BSE), scrapie (in sheep)

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    Description

    Explore the fascinating world of viruses, focusing on their structure, classification, and the life cycle of viral infection. Learn about the capsid, envelope, and how viruses replicate within host cells. This quiz provides insights into the mechanisms that underlie viral behavior and infection.

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